The NEPA process consists of an evaluation of the environmental effects of a federal undertaking including its alternatives.  There are three levels of analysis depending on whether or not an undertaking could significantly affect the environment.  These three levels include: categorical exclusion determination; preparation of an environmental assessment/finding of no significant impact (EA/FONSI); and preparation of an environmental impact statement (EIS).
       At the first level, an undertaking may be categorically excluded from a detailed environmental analysis if it meets certain criteria which a federal agency has previously determined as having no significant environmental impact.  A number of agencies have developed lists of actions which are normally categorically excluded from environmental evaluation under their NEPA regulations.  This will require review and assess applicable to state, local, and federal environmental laws, regulations, and policies.  State and federal information may be obtained from the ITD District Environmental Planner and local regulations can be found at city and county planning departments.
       At the second level of analysis, an environmental assessment (EA) is prepared to determine whether or not a federal undertaking would significantly affect the environment.  If the answer is no, the agency issues a finding of no significant impact (FONSI).  The FONSI may address measures which an agency will take to reduce (mitigate) potentially significant impacts.
       If the EA determines that the environmental consequences of a proposed federal undertaking may be significant, an EIS is prepared.  An EIS is a more detailed evaluation of the proposed action and alternatives.  The public, other federal agencies and outside parties may provide input into the preparation of an EIS and then comment on the draft EIS when it is completed.
       If a federal agency anticipates that an undertaking may significantly impact the environment, or if a project is environmentally controversial, a federal agency may choose to prepare an EIS without having to first prepare an EA.
       After a final EIS is prepared and at the time of its decision, a federal agency will prepare a public record of its decision addressing how the findings of the EIS, including consideration of alternatives, were incorporated into the agency's decision-making process.
EA & EIS Components
       Generally, an EA includes a brief discussion of the following: the need for the proposal; alternatives (when there is an unresolved conflict concerning alternative uses of available resources); the environmental impacts of the proposed action and alternatives; and a listing of agencies and persons consulted.
       An EIS should include discussions of the purpose of and need for the action, alternatives, the affected environment, the environmental consequences of the proposed action, lists of preparers, agencies, organizations and persons to whom the statement is sent, an index, and an appendix (if any).